Serotonin is important in the etiology of mood disorders, and appears to be associated with hormone changes through the life cycle. This study will attempt to measure plasma 5-HIAA at two points in the menstrual cycle of women with and without Late Luteal Phase Dysphoric Disorder (LLPDD). Serotonin levels are anticipated to begin increasing at ovulation in preparation of pregnancy, peaking prior to the onset of menses (maximum level), and decreasing precipitously with the initiation of menstrual flow (nadir) in controls with abnormalities in LLPDD.